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Abstract:

A light emitting diode (LED) and a method for fabricating the same,
capable of improving brightness by forming a InGaN layer having a low
concentration of indium, and whose lattice constant is similar to that of
an active layer of the LED, is provided. The LED includes: a buffer layer
disposed on a sapphire substrate; a GaN layer disposed on the buffer
layer; a doped GaN layer disposed on the GaN layer; a GaN layer having
indium disposed on the GaN layer; an active layer disposed on the GaN
layer having indium; and a P-type GaN disposed on the active layer. Here,
an empirical formula of the GaN layer having indium is given by
In(x)Ga(1-x)N and a range of x is given by 0<x<2, and a thickness
of the GaN layer having indium is 50-200 Å.

Claims:

1. A light emitting device comprising: a first conductive type
semiconductor layer; at least one InxGa1-xN layer
(0<x<0.2) on the first conductive type semiconductor layer; at
least one GaN layer directly on the at least one InxGa1-xN
layer (0<x<0.2); an active layer directly on the at least one GaN
layer; a second conductive type semiconductor layer on the active layer;
and a transparent layer on the second conductive type semiconductor
layer; wherein the at least one InxGa1-xN layer (0<x<0.2)
has a thickness less than 200 Å.

3. The light emitting device according to claim 1, wherein the active
layer comprises at least three layers.

4. The light emitting device according to claim 2, wherein the active
layer comprises a well layer including an InGaN and a barrier layer
including a GaN, and wherein a thickness of the barrier layer is more
than a thickness of the well layer.

5. The light emitting device according to claim 1, wherein an Indium
composition of the at least one InxGa1-xN layer (0<x<0.2)
is lower than an Indium composition of the active layer.

6. The light emitting device according to claim 1, wherein the active
layer includes at least one well layer and at least one barrier layer
formed in 1 period to 7 periods.

7. The light emitting device according to claim 1, further comprising: an
undoped GaN layer having a thickness of 1 μm˜3 μm.

8. The light emitting device according to claim 7, wherein a total
thickness of the undoped GaN layer and the first conductive type
semiconductor layer is 2 μm˜6 μm.

9. The light emitting device according to claim 1, wherein a thickness of
the at least one GaN layer is 10 Å˜30 Å.

10. The light emitting device according to claim 1, wherein the second
conductive type semiconductor layer has a thickness of 750
Å˜1500 Å.

11. The light emitting device according to claim 1, wherein at least one
InxGa1-xN layer (0<x<0.2) is directly on the first
conductive type semiconductor layer.

12. A light emitting device comprising: a first conductive type
semiconductor layer; at least one InxGa1-xN layer
(0<x<0.2) on the first conductive type semiconductor layer; an
active layer on the at least one InxGa1-xN layer
(0<x<0.2) layer; a second conductive type semiconductor layer on
the active layer; and a transparent ITO (Indium-Tin-Oxide) layer on the
second conductive type semiconductor layer; wherein a thickness of the at
least one InxGa1-xN layer (0<x<0.2) is less than a
thickness of the second conductive type semiconductor layer having a
thickness of 750 Å˜1500 Å.

13. The light emitting device according to claim 12, wherein light
generated at the active layer is emitted via the transparent ITO
(Indium-Tin-Oxide) layer to an external.

14. The light emitting device according to claim 12, wherein the active
layer comprises at least three layers.

15. The light emitting device according to claim 12, wherein the active
layer comprises a well layer including an InGaN and a barrier layer
including a GaN, and wherein a thickness of the barrier layer is more
than a thickness of the well layer.

16. The light emitting device according to claim 12, wherein the active
layer comprises a multi-quantum well structure including at least one
dopant in at least one of an at least one well layer or an at least one
barrier.

17. The light emitting device according to claim 12, wherein the active
layer includes at least one well layer and at least one barrier layer
formed in 1 period to 7 periods.

18. The light emitting device according to claim 12, further comprising
at least one GaN layer directly on the at least one InxGa1-xN
layer (0<x<0.2).

19. The light emitting device according to claim 18, wherein a thickness
of the at least one GaN layer is 10 Å˜30 Å.

20. The light emitting device according to claim 12, wherein the second
conductive type semiconductor layer includes at least one well layer and
at least one barrier layer.

21. The light emitting device according to claim 12, wherein the at least
one InxGa1-xN layer (0<x<0.2) has a thickness less than
200 Å.

22. The light emitting device according to claim 12, wherein at least one
InxGa1-xN layer (0<x<0.2) is directly on the first
conductive type semiconductor layer.

23. A light emitting device comprising: a first conductive type
semiconductor layer; at least one InxGa1-xN layer
(0<x<0.2) on the first conductive type semiconductor layer; at
least one GaN layer directly on the at least one InxGa1-xN
layer (0<x<0.2); an active layer on the at least one GaN layer; a
second conductive type semiconductor layer on the active layer, and a
transparent layer on the second conductive type semiconductor layer;
wherein a thickness of the at least one GaN layer is 10 Å˜30
Å.

25. The light emitting device according to claim 23, wherein the active
layer comprises at least three layers.

26. The light emitting device according to claim 24, wherein the active
layer comprises a well layer including an InGaN and a barrier layer
including a GaN, and wherein a thickness of the barrier layer is more
than a thickness of the well layer.

27. The light emitting device according to claim 23, wherein the active
layer comprises a multi-quantum well structure including at least one
dopant in at least one of an at least one well layer or an at least one
barrier.

28. The light emitting device according to claim 24, wherein the at least
one InxGa1-xN layer (0<x<0.2) is directly on the first
conductive type semiconductor layer.

29. The light emitting device according to claim 24, wherein the active
layer is directly on the at least one GaN layer.

30. The light emitting device according to claim 23, wherein a thickness
of the at least one InxGa1-xN layer (0<x<0.2) is less
than a thickness of the second conductive type semiconductor layer having
a thickness of 750 Å˜500 Å.

Description:

[0001] This application is a Continuation of co-pending application Ser.
No. 13/169,887 filed Jun. 27, 2011, which is a Continuation of
application Ser. No. 12/700,720 (now U.S. Pat. No. 7,989,235) filed Feb.
5, 2010, which is a Continuation of application Ser. No. 11/889,549 (now
U.S. Pat. No. 7,682,849) filed on Aug. 14, 2007, which is a Divisional of
application Ser. No. 11/333,247 (now U.S. Pat. No. 7,531,827) filed on
Jan. 18, 2006, and for which priority is claimed under 35 U.S.C.
§120; which is a continuation of PCT International Application No.
PCT/KR2004/001687 filed on Jul. 9, 2004, which designated the United
States, and on which priority is claimed under 35 U.S.C. §120.
Accordingly, this application claims priority of Application No.
2003/48993 filed in Korea on Jul. 18, 2003 under 35 U.S.C. §119. The
entire contents of all of the above-identified applications are hereby
incorporated by reference.

TECHNICAL FIELD

[0002] The present invention relates to a light emitting diode, and more
particularly, to a light emitting diode and a fabrication method thereof
in which a light efficiency can be improved by forming a layer containing
indium (In), whose lattice constant is similar to that of an active layer
formed in the LED.

BACKGROUND ART

[0003] Generally, a light emitting diode (LED) is a kind of semiconductor
device, and it converts an electrical signal into infrared ray or light
by using a characteristic of a compound semiconductor, to send or receive
a signal. The LED is used for home appliances, a remote controller, an
electronic display board, a display device, a variety of automation
apparatuses and the like.

[0004] An operation principle of the LED will be briefly described in the
following.

[0005] When a forward voltage is applied to a semiconductor of a specific
chemical element, electrons and holes are recombined with each other
while moving through a positive-negative junction. The recombination of
the electrons and the holes causes an energy level to fall down, so that
light is emitted.

[0006] The LED is generally manufactured to have a very small size of 0.25
mm2 and is mounted on a printed circuit board (PCB) or a lead frame
using an epoxy mold.

[0007] Representative of the LEDs is a plastic package of 5 mm (T 13/4) or
a new package being developed in a specific application field.

[0008] A color of light emitted from the LED is determined by a wavelength
obtained depending on a combination of elements constituting a
semiconductor chip.

[0009] Particularly, as an information communication apparatus is in a
trend of a small-size and slimness, the communication apparatus has more
miniaturized parts such as a resistance, a condenser, and a noise filter.
The LED is manufactured in a form of a surface mounted device
(hereinafter, referred to as "SMD") so as to be directly mounted on a
printed circuit board (hereinafter, referred to as "PCB").

[0010] Accordingly, an LED lamp for a display device is being developed in
the form of the SMD. Such an SMD can substitute a related-art simple
lamp. The SMD is used for a lamp display, a character display, an image
display and the like that express various colors.

[0011] Further, as a high-density integration technology for a
semiconductor device is developed and a consumer prefers a more compact
electronic product, Semiconductor Mounting Technology (SMT) is widely
used, and a packaging technology of the semiconductor device employs a
technology for minimizing an installation space such as a Ball Grid Array
(BGA), a wire bonding, and a flip chip bonding.

[0012] FIG. 1 is a view illustrating a process for fabricating a light
emitting diode according to the related art.

[0013] As shown in FIG. 1, a gallium nitride (GaN) buffer layer 101 is
formed on a sapphire substrate 100 formed of Al2O3. After that,
a GaN layer 103, which is not doped with dopants (Hereinafter, referred
to as "undoped"), is formed on the GaN buffer layer 101.

[0014] In order to form a Group 3-based element in a form of a thin film
on the sapphire substrate 100 as described above, a metal organic
chemical vapor deposition (MOCVD) is generally used. At this time, the
thin film layer is formed under a constant growth pressure.

[0015] An N-type GaN layer 105 is formed on the undoped GaN layer 103, and
silicon using silane (SiH4) or disilane (Si2H6) gases is
used to form the N-type GaN layer 105.

[0016] After the N-type GaN layer 105 is formed, an active layer 109 is
formed on the N-type GaN layer 105. The active layer 109 functioning as a
light emission region is a semiconductor layer having an illuminant
formed of a indium gallium nitride (InGaN).

[0017] After the active layer 109 is formed, a P-type GaN layer 110 is
subsequently formed.

[0018] The P-type GaN layer 110 is in a contrast to the N-type GaN layer
105. Namely, electrons are drifted by an external voltage in the N-type
GaN layer 105, while holes are drifted by the external voltage in the
P-type GaN layer 110. Therefore, the holes and the electrons are mutually
recombined in the active layer 109, thereby emitting light.

[0019] A transparent metal (TM) layer using a transparent Indium-Tin-Oxide
(ITO) metal is formed on the P-type GaN layer 110 so that light generated
at the active layer 109 is transmitted and emitted to the external.

[0020] After the TM layer is formed, a P-type electrode is formed to
complete the LED.

[0021] However, the LED constructed as above has a drawback in that a
strain is increased due to an inconsistency of the lattice constants
between the InGaN layer of the active layer and the GaN layer, thereby
reducing an amount of light generated in the active layer.

[0022] Further, the inconsistency of the lattice constant deteriorates a
product reliability of the LED.

[0023] Also, there is a drawback in that the active layer, which is formed
on the N-type GaN layer adjacent to the active layer in a form of a
two-dimensional plane, has a lower luminous intensity than a
three-dimensional formation.

DISCLOSURE OF THE INVENTION

[0024] Accordingly, the present invention is directed to an LED and a
fabrication method thereof that substantially obviate one or more
problems due to limitations and disadvantages of the related art.

[0025] An object of the present invention is to provide an LED and a
fabrication method thereof in which a GaN layer having a low
concentration of indium (In) is formed between the active layer and an
N-type GaN layer to reduce an inconsistency of lattice constants between
an active layer and a GaN layer, thereby increasing a light efficiency
and improving a product reliability.

[0026] To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly described, a
light emitting diode includes: a buffer layer disposed on a sapphire
substrate; a GaN layer disposed on the buffer layer; an N-type GaN layer
disposed on the GaN layer; a GaN layer having indium disposed on the
N-type GaN layer; an active layer disposed on the GaN layer having
indium; and a P-type GaN layer disposed on the active layer.

[0027] Here, an empirical formula of the GaN layer having indium is given
by In(x)Ga(1-x)N and a range of x is given by 0<x<2, and a
thickness of the GaN layer having indium is 50-200 Å.

[0028] Also, a GaN layer whose thickness is 10-30 Å is formed on the
GaN layer having indium, and the active layer is of a multi-quantum well
structure having a InGaN/GaN structure.

[0029] Also, a method for fabricating a LED according to the present
invention, includes the steps of: forming a buffer layer on a sapphire
substrate; forming a GaN layer on the buffer layer; forming an N-type GaN
layer on the GaN layer; forming a GaN layer having indium on the N-type
GaN layer; forming an active layer on the GaN layer having indium; and
forming a P-type GaN layer on the active layer.

[0030] Here, after the GaN layer having indium is formed, a GaN layer is
subsequently formed at a thickness of 10-30 Å, and the active layer
is formed in 1 period to 7 periods under a temperature condition of
600-800° C.

[0031] Also, after the active layer is formed, the P-type GaN layer is
formed at a thickness of 750-1500 Å at a temperature of
980-1020° C. A transparent layer is formed around the P-type GaN
layer.

[0032] According to the present invention, the InGaN layer having a low
concentration of indium is formed between the N-type GaN layer and the
active layer formed on the sapphire substrate, so that deterioration of
light efficiency due to inconsistency of a lattice constant between the
GaN layer and the active layer is prevented and the light efficiency can
be improved.

[0033] Also, the InGaN layer having a low Indium composition has a three
dimensional structure on its surface and such three-dimensional growth of
the surface can improve the light efficiency even more.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a view illustrating a process for fabricating an LED
according to the related art;

[0035] FIGS. 2a through 2e are views illustrating a process for
fabricating an LED according to the present invention; and

[0036]FIG. 3 is a view schematically showing a P-type GaN layer formed
according to a quantum well growing method among the method for
fabricating the LED according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0037] Hereinafter, preferred embodiments of the present invention will be
described in detail with reference to accompanying drawings.

[0038] FIGS. 2a through 2e are views illustrating a process for
fabricating a light emitting diode (LED) according to the present
invention.

[0039] As shown in FIGS. 2a through 2e, a buffer layer 201 having an
empirical formula of In(x)Ga(1-x)N is formed on a sapphire
(Al2O3) substrate 200 at a temperature of 500-600° C.,
and an undoped GaN layer 203 is grown up to a thickness of 1-3 μm on
the buffer layer 201 at a temperature of 1000-1100° C. (FIG. 2a).

[0040] Next, an N-type GaN layer 205 is grown up to a thickness of 1-3
μm on the undoped GaN layer 203 at a temperature of 1000-1100°
C. (FIG. 2b).

[0041] After the N-type GaN layer 205 is formed, a GaN layer 207 having a
low mole of indium (In) is grown up at a temperature of 600-800°
C. before an active layer 209 is formed (FIG. 2c).

[0042] The composition ratio of indium in the InGaN layer 207 is given by
In(x)Ga(1-x)N(0<x<0.2). The In(x)Ga(1-x)N(0<x<0.2) layer is
grown up to a thickness of 50-200 Å.

[0043] After the InGaN layer 207 is formed, an active layer 209 is formed.

[0044] The active layer 209 is formed of GaN layer at a thickness of 10-30
Å and makes an electron tunnels into a quantum-well layer, thereby
preventing holes from penetrating into the In(x)Ga(1-x)N(0<x<0.2)
layer.

[0045] The active layer 209 of the InGaN/GaN having a multi-quantum-well
structure is formed in 1 period to 7 periods at a temperature of
600-800° C.

[0046] After the active layer 209 is formed, a P-type GaN layer 210 doped
with a dopant of magnesium (Mg) is formed grown up to a thickness of
750-1500 Å at a temperature of 980-1020° C. A transparent
layer 213 is formed around the P-type GaN layer 210.

[0047]FIG. 3 is a view schematically showing a P-type GaN layer formed
according to a quantum-well growing method among the method for
fabricating the LED according to the present invention.

[0048] As shown in FIG. 3, in the quantum-well growing method, a well
growing step of forming a well layer 301 that includes various dopants
such as In, Ga, and N is performed. Here, a growth condition of the well
layer 301 is given by TMGa: 0-200 μmol/min, TMIn : 0-100 μmol/min ,
NH3: 0-80 L/min, growing temperature: 600-800° C.

[0049] Subsequently, an enough crystal time is given so that the dopants
included in the step of growing the well layer 301 may combine each other
completely to form a crystal layer 302, whereby a combining ability of In
and N, Ga and N, In and Ga inside the well layer 301, is improved.

[0050] Here, a growth time of the crystal layer 302 is given by 0.1 sec-60
min and N2: 30-50 L/min, H2: 30-50 L/min.

[0051] Next, a barrier growing step of forming a barrier layer 303
including various dopants such as Ga, N, is performed. Here, a growth
condition of the barrier layer 303 is given by TMGa: 100-500 μmol/min,
TMIn: 50-200 μmol/min, NH3: 0-80 L/min, growing temperature:
600-800° C.

[0052] As described above, the active layer 209 is formed so as to have a
multi-quantum well structure in the present invention, and the GaN layer
207 having the low concentration of indium is formed in a shallow
thickness on the N-type GaN layer 205 at a low temperature, so that
inconsistency of the lattice constant with the active layer 209 is
reduced and light efficiency can be improved.

[0053] Also, since the InGaN layer of the active layer 209 is formed
through a three-dimensional growth, a brightness of light generated at
the active layer 209 is increased.

INDUSTRIAL APPLICABILITY

[0054] As described above in detail, the present invention forms the InGaN
layer having a low concentration of indium between the N-type GaN layer
and the active layer formed on the sapphire substrate, thereby reducing
inconsistency of the lattice constant with the active layer and improving
light efficiency.

[0055] Further, the InGaN layer having the low concentration of indium,
has a three dimensional structure on its surface, and light efficiency
can be improved even more in case a surface has such a three-dimensional
structure.

[0056] While the present invention has been described and illustrated
herein with reference to the preferred embodiments thereof, it will be
apparent to those skilled in the art that various modifications and
variations can be made therein without departing from the spirit and
scope of the invention. Thus, it is intended that the present invention
covers the modifications and variations of this invention that come
within the scope of the appended claims and their equivalents.

Patent applications by Seong Jae Kim, Seoul KR

Patent applications in class SPECIFIED WIDE BAND GAP (1.5EV) SEMICONDUCTOR MATERIAL OTHER THAN GAASP OR GAALAS

Patent applications in all subclasses SPECIFIED WIDE BAND GAP (1.5EV) SEMICONDUCTOR MATERIAL OTHER THAN GAASP OR GAALAS